Oil seal

ABSTRACT

An oil seal of the type wherein the principal seal is made between the face of a first casing member attached to a rotary shaft or disposed in a machine housing and a flexible washer of a lubricous, high temperature resistant polymer held in place within a second casing and urged axially into engagement with the face of the first casing. The seal assembly is a so-called unitized seal, that is, both the relatively fixed and relatively movable casings are preassembled so that the two-piece unit may be fitted as a whole to a shaft and a machine bore while the unit remains assembled. In one embodiment, the flexible, polymeric sealing washer or ring is urged into engagement with the radial face of the casing by an inclined coil spring. In use, the seal is characterized by low wear, by a hydrodynamic sealing action, by relatively great tolerance to radial runout, and by easy and accurate installation which inherently supplies a desired axial preload to the primary seal components.

United States Patent [1 1 J ackowski 51 Oct. 2, 1973 OIL SEAL {76]Inventor: James E. Jackowski, 1016 S.

Humphrey, Oak Park, Ill.

[22] Filed: Mar. 15, 1971 [211 App]. No.: 124,015

Primary ExaminerSamuel B. Rothberg A!t0rneyJameS T. FitzGibbon 57ABSTRACT An oil seal of the type wherein the principal seal is madebetween the face of a first casing member at tached to a rotary shaft ordisposed in a machine housing and a flexible washer of a lubricous, hightemperature resistant polymer held in place within a second casing andurged axially into engagement with the face of the first casing. Theseal assembly is a so-called unitized seal, that is, both the relativelyfixed and relatively movable casings are preassembled so that thetwopiece unit may be fitted as a whole to a shaft and a machine borewhile the unit remains assembled. In one embodiment, the flexible,polymeric sealing washer or ring is urged into engagement with theradial face of the casing by an inclined coil spring. In use, the sealis characterized by low wear, by a hydrodynamic sealing ac tion, byrelatively great tolerance to radial runout, and by easy and accurateinstallation which inherently supplies a desired axial preload to theprimary seal components.

1 Claim, 6 Drawing Figures PATENIED OCT 2 975 SHEET 1 BF 2 INVENTORJAMES E. JACKOWSKI PATENTEDBBT 2 m 3.762.727

SHEET 2 0F 2 INVENTOR JAMES E. JACKOWSKI ATT'Y 1 OIL SEAL BACKGROUND OFTHE INVENTION The present invention relates to oil seals, and moreparticularly to so-called unitized oil seals, that is, seals of aconstruction wherein both wearing surfaceswhich form the primary sealare contained within the seal unit itself rather than to constructionswherein one surface to be sealed against forms a part of the machinehousing or shaft to be sealed. The seal of the present invention is aso-called end face seal, that is, a sealin which the primary seal ismade against a radially extending, axially facing surface, and, in thepresent invention, the primary seal is a fuorocarbon-to-metal seal, forreasons which will be set forth in detail herein.

Fluid seals, including oil seals, and the like, are known in the priorart, and seals having afluorocarbon primary sealing element are alsoknown in the art. However, it is also well known to those skilled in theart that a number of such prior art seals have presented certainproblems and disadvantages which have not heretofore been able to beovercome, and as a result, it has not always been possible to takefulladvantage of the desirable characteristics of Teflon" oroth erlubricous fluorocarbon materials in constructing fluid seals. Forexample, among the advantages of Teflon or other fluorocarbon polymersare resistance to high temperatures and almost total chemical inertness,with the result that the prospective life of such polymers in use isexceptionally long, from a theoretical standpoint.

Furthermore, polytetrafluoroethylene or similar fluorocarbons or thelike are by their own nature lubricous, and as a result, tend to haveextensive wearinglives in use, and do not present serious problems ofwearing, galling or scoring the surfaces with which theyare associatedin use. However, inthe past, for variousreasons, including certainreasons which will be referred to herein, tetrafluoroethylene or otherfluorocarbon seal units have not proved practical for a wide variety ofinstallations, particularly installations wherein low cost is necessary.

For example, prior art fluorocarbon seals have often been characterizedby rather complex structures, since, by reason of its chemically inertnature, Teflonand its equivalents are not able to be bonded adhesivelyto metal flanges, casings, and the like. Furthermore, Teflon is athermoplastic material rather than an jelastomeric material andtherefore, a major portion of the deflection and defomration which arenecessary to accommodate radial or axial runout or other dimensionalvariation must be supplied by extrinsic forces, such as tensioningsprings, sealing lip or face positioners, or the like. Furthermore,although providing long life in normal use, the finished primary sealingsurface of fluoro carbon sealing elements is soft and non-resilient,rather than elastomeric or resilient, and therefore, if cut, scratchedor nicked during installation, it will retain this condition and willnot provide satisfactory service in use. In other words, scratches orother marks on the wearing face, even when present only to a minorextent, will remain in the surface, and since such poly mers arerelatively non-resilient, as pointed out, the finished element cannotdeform so as to form a proper seal, as a softer rubber might, forexample. Furthermore, rubber, being more flexible, is unlikely to bedamaged in installation, and, as a practical matter, does not presentthis problem at all.

Another drawback which has characterized prior art fluorocarbon seals isthat, because of the lack of elas tomeric character of the Teflonmaterial, close dimensional tolerances must be observed in manufacturingand installation, since, in the event tolerances are too loose, a faultyseal would be developed, and in the event that tolerances were undulytight, excessive force would be presented to the wearing surface. Teflonor the like has practically no ability to accommodate suchirregularities, whereas rubber is very tolerant thereof.

Accordingly, in view of these and other drawbacks, and in view of thetheoretical advantages possible with fluorocarbon seals, an object ofthe present invention is to provide an improved fluorocarbon seal whichwould permit the inherent advantages of a fluorocar bon material to berealized without being characterized by the disadvantages which havebeen associated with this general class of seal in the past.

Another object is to provide an improved Teflon or like fluorocarbonseal in which th ee primary seal is an end face seal.

Anotherobject is to provide a unitized oil seal assembly which mayreadily be installed by relatively unskilled personnel without thedanger of damaging mating parts thereof.

A still further object is to provide a un itized face seal having afluorocarbon or like relatively chemically inert primary seal.

Another object is to provide a seal unit which is characterized byrelatively large tolerance to radial excentricity between the centersrespectively of a bore in a machine housing and a shaft to be sealed.

Another object is to provide a seal assembly which may be fitted to apredetermined axial depth of position in a machine opening by pressingboth casings which make up the assembly with a single tool or in asingle operation, which will thereupon serve to locate the assemblyproperly and simultaneously for subsequent use.

Another object is to provide a seal assembly having one or more of theforegoing advantages and characteristics and characterized in that theTeflon washer portion is carried by and held fixed in relation to theouter casing.

A further object is to provide another form of seal having one or moreof the foregoing advantages, and characterized in that the Teflon washeris held fixed in relation to the inner or shaft-engaging casing of theseal assembly.

A further object is to provide a fluorocarbon seal which is simple toassemble and accordingly, a seal which may be produced at an economicalcost so as to be readily available for widespread use.

Another object is to provide some or all of the fore going advantages ina seal unit having very low friction and low torque lossesand which willprovide excellent sealing performance, including a long life expectancyin use.

Another object is to provide a fluorocarbon containing seal unit havingnovel means for urging the fluorocarbon member into a position ofengagement with a sealing face of an associated portion of the seal.

The present invention provides these and other advantages by providing aunitizedl seal assembly, containing a fluorocarbon primary end face sealmember and having oppositely disposed inner and outer casing elements,wherein the fluorocarbon seal is in the form of an annular member heldin fixed relation to one of said casing elements, and wherein means areprovided for urging the sealing element against an oppositely directed,radially extending face of the other casing element portion of theunitized seal assembly.

The manner in which the foregoing and other inher ent objects andadvantages of the invention are achieved will become more clearlyapparent when reference is made to the following detailed description ofthe preferred embodiments of the invention, and to the drawings, inwhich like reference numbers indicate corresponding parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of oneend of the oil seal unit of the invention;

FIG. 2 is an elevational view of the other end of the assembled sealunit of the invention;

FIG. 3 is a vertical sectional view through a machine housing and anassociated shaft, showing one embodiment of the novel seal unit of theinvention in position of use;

FIG. 4 is a perspective view of the seal unit of the invention withportions broken away, showing both relatively movable parts of the sealin their assembled relation prior to installation thereof with anassociated machine housing and rotary shaft;

FIG. 5 is a perspective view ofa modified form of seal unit according tothe invention, showing portions broken away and showing the unitizedseal in its assembled relation prior to installation; and

FIG. 6 is a greatly enlarged vertical sectional view of the form of sealunit shown in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Although itwill be understood that the invention may be embodied in a number offorms and applied to various uses, the nature of the invention will beillustrated by reference to those embodiments wherein a shaft is to besealed against leakage from oil and wherein the shaft extends through anopening in a machine housing which is bored to receive a shaft andcounterbored to receive the seal.

Thus, referring now to FIG. 1, one form of seal according to theinvention is generally designated 10 and includes a generally radiallyouter casing 12, and'a radially inner casing 14 enclosing other elementsto be described. Referring now to FIG. 3, it is shown that the innersurface 16 of the axially extending flange 18 forming a portion of theinner casing 14 engages the radially outer surface 20 ofa rotary shaft22, and that the axially extending flange 18 is integrally formed with atransition section 24 which is in turn joined to a generally radiallyextending flange 26 having an axially facing inner surface 28. The outercasing 12 is inserted in position of use within the counterbore 30 withthe outer surface 32 of the casing 12 snugly engaging inner surfaces ofthe counterbore 30. A radially inwardly extending flange 34 terminatesin a curl portion 36 in which is received a generally annular one-piecefluorocarbon polymer sealing element 38. The inner margin 40 of thesealing element 38 is locked in place against rotation within the bight42 formed by the curl 36.

In the illustrated embodiments, a flattened helical spring 44 isdisposed between the radially extending axially facing surface 46 of theouter casing 12, and the rear or non-working surface 48 of the sealingelement 38 so as to urge the radially outer margin 50 of the sealingelement against the primary sealing surface 28 of the inner casing 14.By reference to FIG. 3, it will also be seen that inwardly extendinglocking tabs 52 are provided which are struck inwardly from andintegrally formed with axially innermost margins 54 of the outer casing12. Thus, it can be seen that locking the tabs 52 urges the radialflange 26 toward an axially outward position of use, while the spring 44acting through the fluorocarbon sealing element 38 urges the sealingelement 38 and consequently the inner casing 14 in an opposite axialdirection.

Therefore, as assembled, the seal unit 12 will have a maximum axialdimension determined by the forward extent of the margin 54 of flange 56and by the maximum axial movement which thetab 52 permits the radialflange S6 to move. It is also clear that the maximum axial movement inthe opposite direction will be limited by engagement of the flange 26 orthe transition .section 24 with the axially inner portion of the curl 36disposed on the inner margin of the flange 34. In the use of the seal,the desired axial dimension lies between these two extremes, it beingunderstood that flange 26 should desirably not engage the tabs 52 northe curl 36. Having this in mind, another desirable feature of theinvention may be understood, namely, that installation of the seal unitis facilitated by the use of a simple tool T shown in phantom lines inFIG. 3. By reference to FIG. 3, it will be understood that installationoff the unitized seal 10 of the invention is accomplished in a simpleand straightforward manner merely by aligning the outer surface 32 ofthe outer casing 12 with the counterbore 30 with which it will beassociated in use, and, using a tool such as a tool T, pressing the unitaxially inwardly of the bore 30 with a face 58 of the tool T," engagingan oppositely directed face 60 of the flange 34. Since the inner surface16 of flange 18 is sized for a snug but sliding fit over the shaft 22,resistance to axial movement thereof may be overcome by engaging the endsurface 62 of flange 18 with a reduced diameter, axially offset annularface 64 on too] T. Initial fitting of the flange 18 over the shaft 22 isaided by a chamber 66 on the shaft 20 and by a radius 68 on thetransition portion 24 of the inner casing 14.

Referring to a typical installation, such as that illustrated in FIG. 3,it is shown that the face 60 of flange 34 is flush with the surface 70of the machine housing 72 in which the counterbore 30 is formed. FIG. 3also illustrates that flange 18 is disposed such that the end face'62thereof lies slightly axially inwardly of the plane of flange surface60. Accordingly, it may be seen that, in the simplest case ofinstallation, the tool T would be merely a flat ring, and, in thefinally assembled position of use, surfaces 60, 62 and 70 would becoplanar. In another case, such as that which might be brought about bythe use of a tool T" having axially offset surfaces 58 and 64 alreadydescribed, and further including a third offset surface 74, all faces60, 62 and 70 might be in a predetermined axially offset relation toeach other. It is also clear that other combinations of the above couldbe made, including a combination wherein end face 62 would lie axiallyoutwardly of one or both of the surfaces 60, 70.

However, referring to a typical and advantageous use of the seal unit 10of the invention, the parts would desirably be dimensioned so that thedepth of counterbore would have a predetermined minimumdimem sionwithout the need for any maximum, tolerance, depth, that is, the depthof the counterbore 30 might arbitrarily be set so as to be at least0.060 inches larger than the maximum anticipated axial dimension of theflange 56. The tool T would then comprisemerelya large diameter ring,and the surfaces 16, 32, might include a rubber like or resinouscoatingof known type used with voil seals thereon to insure a fluid-tight seal.

For installation, both seal casings 12, 14 are placed in,

the desired alignment, and the tool T is pressed axially until allsurfaces 60, 62 and are flush. This inherently serves to preload thespring 44 to a desired extent, and provides a sufficient axial workingclearance between tabs 52 and the outer margins of flange 26, while thesurface 28 is gently but firmly pressed against the margin 50 of thesealing element 38.

By reference to the foregoing, it will be appreciated that the sealingelement 38 has been protected against the possibility of being scratchedor damaged during installation, since the preassembled r casings l2, 14,which are held together by tabs 52, serve to surround and protect theelement 38. Provision of the radius 68 facilitates initial alignment ofthe inner casing .14 with the shaft 22, and inasmuch as the primary sealis an end face seal rather than a radialor lip seal, relatively greatradial runout of the shaft 22 relative to bore 30 can be accommodatedwithout compromise of sealing effectiveness.

Another feature of the invention is the provision of the inclinedhelical spring 44. Although other forms of springs are useful with theinvention, a helical spring of this type, while known per se, has notheretofore been believed to have been used in applyingan axial force,

against a sealing element of an end face type seal. Such a spring is notonly economical, but tends to be self centering, it need not be fastenedto the flange 12 to be retained in place, and it exertsa relativelyconstant,

uniform pressure throughout its circumferential extent.

trated relation, the tabs 52 are struck inwardly to form,

the unitized seal into an assembled but not rigid unitary relation.Since the primary seal is a fluorocarbon-tometal seal, the seal ischaracterized by low starting torque, low friction, and substantialself-lubrication.

Referring now to FIGS. 5 and 6, another form of seal unit 76 accordingto the invention is shown to include an outer casing 78 and an innercasing 80, the latter including a. radially inwardly facing, annularsurface 82, while the outer casing 78 includes a radially outwardlyfacing, circumferentially extending surface 84 formed on an axiallyextending flange 79.

FIG. 6 shows that the inner casing 80 includes a generally axiallyextending flange 86, on which surface 82 is formed, a plurality of tabs88 (one, only shown in FIG. 6) for engaging an inner margin 90.0f theradial flange 92 of the outer casing 78. An inner casing radial flange94 extends outwardly from the axial flange 86 and terminates in a curl96 having a bight 98 receiving the radially. outer margin 100 of theannular sealing element 102 which is also in the form of a flexible butgenerally non-resilient fluorocarbon washer. One axial face 104 of thesealing element 100 engages an inner axial face 106 of the radial flange92, while the opposite face 108 thereof is engaged by the spring 110which is backed up by radial flange 94 and which therefore urges theelement 102 into sealing engagement against the surface 106 of flange 92with a predetermined force.

In this embodiment, the spring 110 is also preferably an inclinedhelical spring which acts principally axially rather than radially. Asin the other embodiment, the axial flange 79 is engaged in a snugsealing relation with a counterbore 112, while the inner surface 82 fitssnugly over the outer surface 114 of a rotatable shaft 116.Theernbodiment of FIGS. 5 and 6, the inner casing 80 and its associatedelements are rotated in use and hence are subjected to centrifugalforce; however, since the primary sealing surface 104 of the element 102is located radially inwardly of the bight 98 locking the element inplace, centrifugal force, to the extent that it is effective, tends todraw the inner margin 118 of the sealing element 102 more tightlyagainst the surface 106 of flange 92 rather than tending to separate theelement 102 from the flange 92. Furthermore, centrifugal force tends tourge the spring radially outwardly, causing any forces thus generated toact to push the inner margin 1180f the element into tighter engagementwith the flange 102.

In other respects, the unitized seal unit 76 of FIGS. 5 and 6 is similarto the embodiment shown in FIGS. 1-4. A tool T is used in the samemanner for installation to a desired, predetermined position within thecounterbore 112. In reference to FIGS. 3 and 5, it will be appreciatedthat, in use, there is ordinarily a small but definite working clearancebetween the tabs 52, 88 andthe radial flanges 26, 92, so that the tabs52, 88 hold the sealunits 10, 76 in their preassembled or unitized formsprior to installation, but preferably do not frictionally engage eachother after installation.

In use, seals of this type are competitive from a cost standpoint withvery large diameter lip seals, which are commonly molded seals, sincemolds for forming very large diameter seals are quite expensive.Accordingly, seals of the described type are useful and competitive withother seals when applied to engine crankshafts and 1 other likeapplications. In use, it has been found that a hydrodynamicactionoccurs, that is, the oil film wetting the surfaces 28, 106 tendsto lift the fluorocarbon element 38, 102 very slightly off the surfaces28, 106, thereby permitting high peripheral linear speeds, such as 6,000feet per minute or more, without rapid wear or overheating.Nevertheless, the constructions illustrated provide excellent staticseal characteristics and therefore resist leakage even when the engineor other assembly with which they are associated are not in use.

It will thus be seen that the present invention provides easilyinstalled unitized oil seal assemblies having fluorocarbon sealingelements and having a number of advantages and characteristics,including those referred to herein and others which are inherent in theinvention. I

It is anticipated that a number of modifications and variations of thedesired embodiments will occur to those skilled in the art and suchchanges may be made without departing from the spirit of the inventionof the scope of the appended claims.

I claim:

1. An end face oil seal assembly for maintaining a fluid-tight sealbetween two relatively movable parts comprising, in combination, innerand outer casing elements, a sealing element comprised of a fluorocarbonmaterial, and spring means for urging said sealing element in agenerally axial direction, one of said casing elements having agenerally circumferentially extending flange portion with a given axialextent, and the other of said casing elements also having a generallycircumferential flange portion with a given axial extent, each of saidcasings also having generally radially extending flanges which areaxially spaced apart and disposed with the inner surfaces thereof in atleast partially axially facing relation to each other, one of said axialflanges having a face adapted to be received in snug sealing engagementwith a portion of a machine housing and the other of said axial flangeshaving a face adapted to be received by a portion of a relativelyrotatable shaft, said sealing element being a single element, beingdisposed within the space defined between said inner sur-faces of saidradial flanges, and having one marginal portion thereof locked againstrelative motion with respect to said outer casing element, and a secondmarginal portion of said sealing element being adapted to engage saidinner surface of said radial flange of said other casing to form aprimary end face seal therewith, saidd spring means being disposedwithin said defined space and urging said second margin of said sealingelement axially into engagement with said inner surface of said radialflange, said assembly further including means on one of said casings forengaging a portion of the other of said casings to prevent axialseparation thereof.

1. An end face oil seal assembly for maintaining a fluid-tight sealbetween two relatively movable parts comprising, in combination, innerand outer casing elements, a sealing element comprised of a fluorocarbonmaterial, and spring means for urging said sealing element in agenerally axial direction, one of said casing elements having agenerally circumferentially extending flange portion with a given axialextent, and the other of said casing elements also having a generallycircumferential flange portion with a given axial extent, each of saidcasings also having generally radially extending flanges which areaxially spaced apart and disposed with the inner surfaces thereof in atleast partially axially facing relation to each other, one of said axialflanges having a face adapted to be received in snug sealing engagementwith a portion of a machine housing and the other of said axial flangeshaving a face adapted to be received by a portion of a relativelyrotatable shaft, said sealing element being a single element, beingdisposed within the space defined between said inner sur-faces of saidradial flanges, and having one marginal portion thereof locked againstrelative motion with respect to said outer casing element, and a secondmarginal portion of said sealing element being adapted to engage saidinner surface of said radial flange of said other casing to form aprimary end face seal therewith, saidd sPring means being disposedwithin said defined space and urging said second margin of said sealingelement axially into engagement with said inner surface of said radialflange, said assembly further including means on one of said casings forengaging a portion of the other of said casings to prevent axialseparation thereof.